1. Field of the Invention
The invention relates to a method and apparatus for heart stimulation and/or diagnosis of the type wherein the polarity and duration of voltage applied to the heart can be varied.
2. Description of the Prior Art
Devices for heart stimulation, especially as implants but also for external placement, are known in a wide range of variations. The most common is the pacemaker, which by the controlled application of electrical pulses to the heart can control the beating of the heart, either completely when the heart's natural pumping function is lost due to disease or impairment, or as a controlled supplement to intermittent natural beating. A pacemaker is often designed with the capability of also affecting a defibrillation function, i.e., for emitting powerful current shocks intended to break an unsuitable arrhythmic state (e.g. fibrillation). This is a rather forceful method of treatment and for many years there has been a desire to achieve gentler means of terminating and preventing such states.
In commonly occurring malfunctions of the heart muscles, instead of a consistent "ignition sequence" propagating in a natural manner from the sinus node to produce a satisfactory heartbeat, there is a type of cyclical process which does not dissipate after a full contraction but can continue as local contractions to no purpose. The conduction system has collapsed. A relatively mild therapy for correcting or restoring this system is desirable.